Project Raster Data

To project data that is associated with a geographic raster reference object, first create a grid of latitude-longitude coordinates for each point in the raster. Then, project the geographic coordinates tox-ymap coordinates.

For example, import elevation raster data as an array and a geographic cells reference object. Get the latitude-longitude coordinates for each point in the raster by using thegeographicGridfunction.

[Z,R] = readgeoraster('n39_w106_3arc_v2.dt1'); [lat,lon] = geographicGrid(R);

Now that you have your grid, select a map projection to use when projecting the coordinates. For this example, create aprojcrsobject for UTM zone 13 in the northern hemisphere. Then, project the latitude-longitude coordinates tox-ycoordinates.

p = projcrs(32613); [x,y] = projfwd(p,lat,lon);

Display the projected raster as a surface by callingmapshowand specifying thex-ycoordinates and elevation array. Add axis labels and apply a colormap appropriate for elevation data.

图mapshow (x, y, Z,'DisplayType','surface') xlabel('x (meters)') ylabel('y (meters)') demcmap(Z)

If the geographic CRS of the latitude-longitude coordinates does not match the geographic CRS of the projected CRS, then the projected coordinates may be inaccurate. You can find the geographic CRS of aprojcrsobject or a geographic raster reference object by querying theirGeographicCRSproperties.

p.GeographicCRS.Name

ans = "WGS 84"

R.GeographicCRS.Name

ans = "WGS 84"

The DTED file used in this example is courtesy of the US Geological Survey.

Unproject Raster Data

To unproject data that is associated with a map raster reference object, first create a grid ofx-ycoordinates for each point in the raster. Then, unproject thex-ymap coordinates to geographic coordinates.

For example, import an image of Boston as an array and a map cells reference object. Get information about the map projection as aprojcrsobject by querying theProjectedCRSproperty of the reference object.

[Z,R] = readgeoraster('boston.tif'); p = R.ProjectedCRS;

Get thex-ycoordinates for each point in the raster by using theworldGridfunction.

(x, y) = worldGrid (R);

Unproject thex-ycoordinates to latitude-longitude coordinates by using theprojinvfunction and specifying theprojcrsobject and coordinate grid.

[lat,lon] = projinv(p,x,y);

Display the unprojected image by callinggeoshowand specifying the latitude-longitude coordinates and image array. By default,geoshowdisplays coordinates using a Plate Carrée projection. Then, add axis labels.

figure geoshow(lat,lon,Z) xlabel('Longitude (degrees)') ylabel('Latitude (degrees)')